John Donegan-NY-late 1800's

Looking for any info on John Donegan, wife Kate Tiernan, at least one son, Joseph Donegan.Joseph was born June 17, 1890 in New York City.Joseph had at least one more brother and a sister, but I can't find them.Where did John and Kate come from, or were they born in NY?Who were their parents?Who are their other children?Joseph was my g-grandfather, and he died in Flushing, NY. Help!!!!